Multiple propeller ducted system

ABSTRACT

A ducted propulsion system for waterborne, semi-submerged or fully submerged vessels comprising a ducted system having two or more intake ducts which open below the mid depth of the vessel, and which merge into a specially shaped non-circular composite duct which generally extends in the fore and aft direction of the vessel. Propeller means are mounted independently in the composite duct and adapted to induce a flow of water through the system of ducts to propel said vessel. The propeller means comprise two or more propellers or impellers each having its own independent shafting, bearings and supporting structure.

United States Patent Doust [451 May 16, 1972 [54] MULTIPLE PROPELLERDUCTED SYSTEM [72] Inventor: David John Doust, 276 St. James St. W.,

FOREIGN PATENTS OR APPLICATIONS 1,112,686 3/1956 France ..l15/l6 287,2537/1931 Italy ..1l5/39 Primary Examiner-Milton Buchler AssistantExaminerCarl A. Rutledge Attorney-Jerry B. Cesak [57] ABSTRACT A ductedpropulsion system for waterborne, semi-submerged or fully submergedvessels comprising a ducted system having two or more intake ducts whichopen below the mid depth of the vessel, and which merge into a speciallyshaped non-circular composite duct which generally extends in the foreand aft direction of the vessel. Propeller means are mountedindependently in the composite duct and adapted to induce a flow ofwater through the system of ducts to propel said vessel. The propellermeans comprise two or more propellers or impellers each having its ownindependent shafting, bearings and supporting structure.

18 Claims, 27 Drawing Figures PATENTEDHAY 16 m2 SHEET 1 [IF 9 FIG. 1

INVENTOR I 3 David John DOUST PA TEN (JIL'N TS PHE'NTEDMAHSM 3.662.702

SHEETEUFQ INVENTOR David John DUUST imwv PA T AGENTS P'A'TENTEBHAY 16 m2SHEET 3 OF 9 PATENTEDMAY 16 m2 SHEET k 0F 9 HAPELLER t SECrIoN INVENTORDavid John DOUST 7m 7 PAT T AGENTS PRTENTEUMAY 1s m:

SHEET 5 [1F 9 MF'ELLER SECTlO MEQ IN DIFFUSE R SECTION t VESSEL INVENTORDavid John DOUST jmv fia 4X PATENT AGENTS INVENTOR David John DOUSTPA'TE'N'TEDnmsm 3.662.702

SHEET 8 BF 9 DlFFUSER 'SEC'TKDN INVENTOR David John DOUST AT AGENTSPATENTEDMHBM: 3.662.702

SHEET 9 OF 9 INVENTOR David John DOUST PATE T AGENTS MULTIPLE PROPELLERDUCTED SYSTEM This invention relates to a new and improved propulsionand steering apparatus for use with waterborne, semi-submerged or fullysubmerged vessels.

Conventional propellers working outside of a ships hull can be adverselyaffected by the following factors:

a. Breakdown of flow into the propeller or propellers, especially in thecase of full-bodied vessels such as tankers, ore and bulk carriers;

b. Vibration of the hull structure due to propeller-excited pulsationsarising from the flow irregularities exaggerated by item (a);

c. Loss of propulsive efficiency at high thrust loadings, rates ofrotation and input shaft powers which physically restrict the speedperformance of large vessels and largely determine the choice betweensingle, twin or multiple combinations;

d. Loss of manoeuvrability and rudder action due to the blanking effectof the after body shape on the flow into the rudders;

e. Loss of stopping ability and reverse propeller thrust on the vessel,making the problem of stopping and taking avoiding action very difficultin the case of super-tankers and other large vessels;

f. Liability of damage to propeller or propellers working outside theconfines of the hull surface, due to contact by ice, floating hazards orother vessels.

According to the present invention, there is provided a ductedpropulsion system for waterborne, semi-submerged or fully submergedvessels comprising a ducted system having two or more intake ducts whichopen below the mid depth of the vessel, and which merge into a speciallyshaped non-circular composite duct which generally extends in the foreand aft direction of the vessel, propeller means mounted independentlyin said composite duct and adapted to induce a flow of water throughsaid system of ducts to propel said vessel, said propeller meanscomprising two or more propellers or impellers each with its ownindependent shafting, bearings and supporting structure.

By fitting such a series of two or more propellers or impellers,longitudinally spaced along the composite duct, it is possible toincrease the total power absorption of the overall propulsion systemwithout the attendant disadvantages of multi-conventional propellersystems exposed outside of the hull surface of the vessel.

Due to the configuration of the composite duct, it is also possible toprovide for power absorption from the main propulsion machinery inexcess of that which can be absorbed by a single propeller working in acircular duct, thus resulting in increased thrust available forpropulsion of the vessel.

The mechanical complications of co-axially mounted, contra-rotatingpropellers are also largely overcome by driving the multi-stage seriesof propellers independently and mounting them non-coaxially in thecomposite duct.

The invention will be further described by way of example only withreference to the embodiments illustrated in the accompanying drawings,wherein:

FIG. I is a schematic drawing of the duct system;

FIG. 2 is a sectional detail view of the inlet section of the duct;

FIG. 3 is a sectional detail view of the inlet grid;

FIG. 4 is a sectional detail plan view of the inlet fairing;

FIG. 5 is a sectional view on the line 5-5 of FIG. 4;

FIG. 6 is a sectional detail plan view of the valve section of the duct;

FIG. 7 is a sectional view on the line 7-7 of FIG. 6;

FIG. 8 is a sectional detail plan view of the transition section of theduct;

FIG. 9 is a series of section views on the line V-V, W-W and X-X ofFIG.8;

FIG. 10 is a sectional detail plan view of the merging section of theduct;

FIG. 11 is a sectional view on the line 11-11 of FIG. 10;

FIG. 12 is an isometric view of the merging section;

FIG. 13 is a sectional plan view of the impeller section of the duct;

FIG. 14 is a detail of the shaft support;

FIG. 15 is a sectional view on the line 15-15 of FIG. 13;

FIG. 16 is a sectional plan view of a modified impeller section of theduct;

FIG. 17 is a detail of the shaft supporters;

FIG. 18 is a sectional view on the line 18-18 of FIG. 16;

FIG. 19 is a sectional view on the line 19-19 of FIG. 16;

FIG. 20 is a sectional plan view of the diffuser section;

FIG. 21 is a series of sectional views on the lines P-P, Q- Q and T-T ofFIG. 20;

FIG. 22 is a sectional plan view of the rudder section;

FIG. 23 is a sectional view on the line 23-23 of FIG. 22;

FIG. 24 is a detail view of the exit grid bars;

FIG. 25, 26 & 27 illustrate various methods of noise and vibrationattenuation.

Referring to the drawings, a vessel 11 is provided with a ductedpropulsion system comprising two intake ducts 12 opening from the sidesof the vessel and extending inwards and aft to merge into a commoncomposite duct 13 the exit end of which opens into a rudder section orexpansion nozzle 14. A third intake duct opening from the bottom of thevessel may be provided if desired; however, such a duct is not shown inthe drawings.

Each intake duct is of non-circular cross-section with specialtriangulated recessing provided at their after extremities to avoid highentry hydraulic losses in the overall system. Each of the intake ducts12 is also provided with conventional flow restricting means ofsubstantially rectangular cross-section, to vary the effective flow ofwater, through said ducts by varying the cross-sectional area of theducts.

In order to increase the permissible power input to a particular vesseland without the complication of conventional multiple/twin-screw shafts(A-bossings) exposed outside of the ship surface, two or more impellersmay be mounted noncoaxially mounted within the common duct 13. Note thatwith the composite duct system indicated, impeller clearances are muchless critical than for a regular duct and concentric coaxial impeller,and produces improvements in propulsion efficiency of between 5 and 10percent relative to a single impeller.

The propellers are mounted in the mid portion of the composite duct 13,these propellers are spaced longitudinally at intervals in the duct. 7

Each propeller or impeller is separately mounted on a shaft and may bedriven independently or through a common gear box or propulsion motor,depending on the particular application of the system. I

Greatly increased lateral control of the vessel when going astern isachieved by throttling the flow in either of the Y-intake ducts 12. Thiscan be further improved by the use of controlled pitch impellers.

FIG. 1 is a diagrammatic layout of the ducted propulsion system or as itis called the YPASS Propulsion System". The various sections aredesignated in FIG. 1 as follows:

Section A Inlet Section Section B Valve Section Section C TransitionSection Section D" Merging Section Section E" Impeller Section Section FDiffuser Section Section G" Rudder Section Each of these sections isdescribed separately.

INLET SECTION The duct inlet is illustrated in FIG. 2. The width of theduct is shown as a. Inlet grids 14 are spaced across the front of theinlet 15. These grids protect the inlet ducts from ice or submergedobjects. Details of the cross-section of the grids are shown in FIG. 3.It has been found that to avoid high frictional losses the width b ofthe triangular grid preferably is from about 0.l inches to about 0.1aand the spacing between the grid bars is preferably from about 0.1a toabout a.

It has been determined that conic development recesses give the minimumfriction entry losses into such a system. The angle of entry at of therecessed cone fairing 16 which is shown in FIGS. 2 and 4 may vary fromabout to about 60 with the optimum angle varying from about to 40depending on the local lines of the vessel in way of the ducted inlet. Agood average design value appears to be about 30 for a vessel of averageafter body fullness. The dimension d which is the depth of the inletfairing 16 may vary from about 0 to about 0.5a. FIG. 5 illustrates thecross-section of the inlet fairing l6 taken on the line 5-5 on FIG. 4.

VALVE SECTION The valve section of the duct is illustrated in FIG. 6.The valve 17 is shown in the open position in full lines and in theclosed position in broken lines. FIG. 7 is a detail of the valve 17 andshows the valve mounted on a shaft 18 which is sup ported from above.The valve 17 could, of course, be mounted on a shaft passing through theduct to give a top and bottom support for the valve. This can be done asdesired. If desired, the corners of the duct can be rounded. The valueof e which is the radius of the corners of the duct in the valve sectionshould be selected to be in the range of from about 0 to less than 0.5 Va -l'h where a is the width of the duct and h is the height of the ductat the valve section.

TRANSITION SECTION The transition section of the duct which is locatedbetween the valve section and the merging section is illustrated inFIGS. 8 and 9. It has been found advantageous in order to efficientlycontrol the flow of water without causing choking at the intersection tolimit the radius j of the corner of this section by the followingformula:

The length transition section L is greater than the width of the ducta".

FIG. 9 shows the manner which the cross'section of the transitionsection changes from a more or less rectangular section at x to asection which has a flat surface on one side and a semi-circular surfaceat the other. At the point at which the transition section joins thevalve section, at line XX, the cross-section of the duct is rectangularwith the corner radius being equal to e which was defined above. Movingalong the transition section the surface of the duct on the inside or onthe Y-side does not change. In other words, it remains flat with smallradius corners. The surface of the duct on the outside of the Ygradually changes into a curved section, the radius of which isdetermined by the formula given above. At the point at which thetransition section joins the merging section, the outer surface of theduct is semi-circular.

MERGING SECTION The merging section in which the two separate inletducts l2 merge into a common duct 13 is illustrated in FIGS. 10, 11 and12. The ratio of the area of the inlet ducts in relation to the area ofthe common ducts is dependent of the speed of advance of the vessel, itssize and shape. Generally, it has been found that the width of thecommon duct w should be greater than a, the width of the single duct. Inaddition, it has also been found that the cross-sectional area of thecomposite duct must not be greater than the combined cross-sectionalareas of the inlet ducts.

For optimum results, the angle 13" which is the angle that the centerline of the separate inlet ducts makes with the center line of thevessel, should be selected to be in the range of from about to about 60.The width of the joining piece It between the two ducts, should be equalto or less than w", the width of the common duct. This joining piece 39is a watertight structural member which is flat to simplify mounting ofthe impeller shaft stuffing boxes and bearings. A fairing piece 40 whichneed not be watertight is located aft of the joining piece 39 tostreamline the flow of water through the ducts.

IMPELLER SECTION The impeller section is shown in FIGS. 13 to 19. FIG.13 is a plan view of an impeller section in which there are located twoimpellers 20. The impellers may be staggered one in front of the otheras is shown or they may be mounted side by side. Each impeller is drivenby its own independent shaft. The shafts are supported on shaft supports21 which are shown-in detail in FIG. 14. The impellers 20 would normallybe operated so that the impellers were contra-rotating and were out ofphase with each other. The clearance which has been found on these verylarge impellers is surprisingly little and a maximum of 3 inches hasbeen found to be required. Usually considerably less than this isneeded.

To reduce the wear of the walls of the duct, wear inserts 22 areinserted into the walls of the duct at those places at which thepropellers come close to the walls and at which wear would normally bequite high. 7

It has been found that the number of blades in the propeller can bevaried considerably depending on the type of vessel in which the ductedpropulsion system is used. Usually, the number of blades varies fromabout three to seven.

FIG. 16 illustrates an impeller section in which there are threeimpellers 23, each mounted on its own independent drive shaft. In thiscase, the impellers are staggered so that two are along side of oneanother and the center one is placed forward of the other two. I

In such an arrangement, the shaft supports 24, which are illustrated inFIG. 17, would normally be located above and below the shaft. Wearinserts 25 may be fitted about the periphery of the duct in line withthe impellers which are located in a side-by-side arrangement.Additional wear inserts 26 may be located at the top and bottom of theduct as is illustrated in FIG. 18 at the point at which the forwardimpeller approaches the surface of the duct.

FIG. 19 shows the arrangement of the three impellers two of whichoperate in a clockwise direction and the third impeller operates in acounter-clockwise direction. The propellers are mounted on the shaft sothat they are out of phase with each other.

The cross-section of the duct in the impeller section is illustrated inFIG. 19. The two side walls'are semi-circular to fit the contour of theimpellers or propellers mounted within them. The top and bottom surfacesare flat.

DIFFUSER SECTION FIGS. 20 and 21 show the diffuser section andillustrate how the duct cross-section varies at this section. The sidewalls of the duct in the impeller section are semi-circular and the topand bottom walls are flat. In the difiuser section the cross-sectionbecomes rectangular. At the start of the diffuser section the radius inthe corners is h/2 where h is the height of the duct. At the end of theditfuser section, the cross-section of the duct is rectangular. Theradius at the corners gradually changes and is determined by the formulax (h/2) (u/H) where h is the length of the diffuser section and 14" isthe distance from the end of the diffuser section to the point at whichthe radius is to be calculated. The length of the diffuser section isshown as H.

RUDDER SECTION dem rudder arrangement is further increased by the use ofcontrolled pitch impellers. The cross-section at the rudder section isshown in FIG. 23 and is rectangular.

A series of grids are spaced across the aft end of the duct to protectthe rudders. Details of the grid bars are given in FIG. 24. The numberof rudders used varies greatly again with the type of vessel. It isenvisaged that anywhere from two to rudders can be used to advantage.

NOISE AND VIBRATION ATTENUATION The ducted propulsion system of thepresent invention can be modified to modulate the noise emissionexternal to the ship. Various ways of doing this are shown in FIGS. 25,26 and 27.

FIG. 25 illustrates one method by which noise and vibration may becontrolled. The left-hand side of the figure is a crosssection of theship with the hull 32 being shown and the duct wall 33. The right-handpart of the drawing is a longitudinal cross-section and the transversemembers 35 are shown. Damping material 36 can be adherred to theexterior surface of the duct walls 33 in order to reduce the noise andvibration.

FIG. 26 again shows a cross-section of the duct, the lefthand side ofthe drawing being a section across of the ship and the right-hand sideof the drawing being a longitudinal crosssection. Acoustic absorptivematerial 37 is adherred to the exterior wall of the duct 33, the hull 32and the transverse members 35 to provide noise and vibration control.

FIG. 27 illustrates the use of acoustic insulation. In this case, thevoid between the hull 32 and the duct 33 is filled with acousticinsulation 18 again to reduce noise and vibration.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A ducted propulsion system for waterborne, semisubmerged or fullysubmerged vessels comprising a duct system having two or more intakeducts which open below the mid depth of the vessel and which merge intoa composite duct generally extending in the fore and aft direction ofsaid vessel, each of said inlet ducts consisting of:

an Inlet Section a Valve Section, and a Transition Section said inletsection having a recessed cone fairing at its after end which makes anangle of less than 60 with the hull, and a plurality of grids spacedacross the inlet,

said valve section having a valve adapted to throttle, the

flow of water through said inlet duct and said transition section havinga cross-section which gradually changes from the cross-section of thevalve section to the cross-section of the merging section,

said inlet ducts join together to form a single composite duct at themerging section, the angle between said separate inlet ducts and thecenter line of the ship being in the range of from about to about 60said composite duct consisting of an impeller section in which there ismounted propeller means adapted to induce a flow of water in said ductsystem, said propeller means comprising two or more propellers orimpellers each having its own independent shafting bearing andsupporting structure, the side walls of the duct forming said impellersection being semi-circular and the top and bottom being flat a diffusersection in which the cross-section of the duct changes gradually fromthat of the impeller section to a rectangular cross-section and a ruddersection having a rectangular cross-section adapted to house a pluralityof rudders and a series of grids spaced across the aft end of said duct.

2. The ducted propulsion system as claimed in claim 1 having two inletducts which open from the sides of the vessel.

3. The ducted propulsion system as claimed in claim 1 in which there arethree inlet ducts, two opening from the sides of the vessel and oneopening from the bottom of the vessel.

4. The ducted propulsion system as claimed in claim I in which thecross-sectional area of of the composite duct is not greater than thecombined cross-sectional areas of said inlet ducts.

5. The ducted propulsion system as claimed in claim 1 in which saidrecess cone fairing makes an angle of between 10 and 40 with the hull.

6. The ducted propulsion system as claimed in claim 1 in which there aretwo impellers mounted in a side-by-side relationship.

7. The ducted propulsion system as claimed in claim 1 in which there aretwo impellers which are mounted one in front of the other in a staggeredrelationship.

8. The ducted propulsion system as claimed in claim 1 in which there arethree impellers, two of which are mounted along side of each other andthe third is mounted between the other two and out of line with them.

9. The ducted propulsion system as claimed in claim 1 in which theimpellers are contra-rotating.

10. The ducted propulsion system as claimed in claim 1 in which thenumber of rudders is from two to ten.

11. The ducted propulsion system as claimed in claim 1 in which soundand vibration absorptive material is placed about the ducts to modulatenoise emission.

12. A ducted propulsion system for waterborne, semi-submerged or fullysubmerged vessels comprising a duct system having at least two intakeducts which open below the mid depth at the sides of the vessel andmerge into a composite duct extending toward the stern, each of saidinlet ducts including an inlet section, a valve section and a transitionsection, a valve in said valve section adapted to throttle the flow ofwater through the inlet duct, said transition section having across-section which gradually changes from that of the valve section tothat of the merging section, and inlet ducts joining together to form asingle composite duct at the merging section, said composite ductincluding an impeller section, a diffuser section and a rudder section,propeller means provided in said impeller section and including at leasttwo propellers for inducing a flow of water through the duct system,said diffuser section having a cross-section which gradually changesfrom that of the impeller section to that of the rudder section, and aplurality of rudders provided in the rudder section.

13. The ducted propulsion system as claimed in claim 12 in which thecross-sectional area of the composite duct is not greater than thecombined cross-sectional areas of said inlet ducts.

14. The ducted propulsion system as claimed in claim 12 in which the twopropellers are disposed in a side by side relationship in said impellersection.

15. The ducted propulsion system as claimed in claim 12 in which the twopropellers are mounted one in front of the other in a staggeredrelationship.

16. The ducted propulsion system as claimed in claim 12 in which thereare three propellers in said impeller section, two of the propellersbeing disposed in a side by side relationship and the third beingdisposed between the other two and out of line with them.

17. The ducted propulsion system as claimed in claim 12 in which saidpropellers are contra-rotating.

18. The ducted propulsion system as claimed in claim 12 together withsound and vibration absorptive material placed about the ducts tomodulate noise emission.

1. A ducted propulsion system for waterborne, semisubmerged or fullysubmerged vessels comprising a duct system having two or more intakeducts which open below the mid depth of the vessel and which merge intoa composite duct generally extending in the fore and aft direction ofsaid vessel, each of said inlet ducts consisting of: an Inlet Section aValve Section, and a Transition Section said inlet section having arecessed cone fairing at its after end which makes an angle of less than60* with the hull, and a plurality of grids spaced across the inlet,said valve section having a valve adapted to throttle, the flow of waterthrough said inlet duct and said transition section having across-section which gradually changes from the cross-section of thevalve section to the cross-section of the merging section, said inletducts join together to form a single composite duct at the mergingsection, the angle between said separate inlet ducts and the center lineof the ship being in the range of from about 20* to about 60* saidcomposite duct consisting of an impeller section in which there ismounted propeller means adapted to induce a flow of water in said ductsystem, said propeller means comprising two or More propellers orimpellers each having its own independent shafting bearing andsupporting structure, the side walls of the duct forming said impellersection being semi-circular and the top and bottom being flat a diffusersection in which the cross-section of the duct changes gradually fromthat of the impeller section to a rectangular cross-section and a ruddersection having a rectangular cross-section adapted to house a pluralityof rudders and a series of grids spaced across the aft end of said duct.2. The ducted propulsion system as claimed in claim 1 having two inletducts which open from the sides of the vessel.
 3. The ducted propulsionsystem as claimed in claim 1 in which there are three inlet ducts, twoopening from the sides of the vessel and one opening from the bottom ofthe vessel.
 4. The ducted propulsion system as claimed in claim 1 inwhich the cross-sectional area of of the composite duct is not greaterthan the combined cross-sectional areas of said inlet ducts.
 5. Theducted propulsion system as claimed in claim 1 in which said recess conefairing makes an angle of between 10* and 40* with the hull.
 6. Theducted propulsion system as claimed in claim 1 in which there are twoimpellers mounted in a side-by-side relationship.
 7. The ductedpropulsion system as claimed in claim 1 in which there are two impellerswhich are mounted one in front of the other in a staggered relationship.8. The ducted propulsion system as claimed in claim 1 in which there arethree impellers, two of which are mounted along side of each other andthe third is mounted between the other two and out of line with them. 9.The ducted propulsion system as claimed in claim 1 in which theimpellers are contra-rotating.
 10. The ducted propulsion system asclaimed in claim 1 in which the number of rudders is from two to ten.11. The ducted propulsion system as claimed in claim 1 in which soundand vibration absorptive material is placed about the ducts to modulatenoise emission.
 12. A ducted propulsion system for waterborne,semi-submerged or fully submerged vessels comprising a duct systemhaving at least two intake ducts which open below the mid depth at thesides of the vessel and merge into a composite duct extending toward thestern, each of said inlet ducts including an inlet section, a valvesection and a transition section, a valve in said valve section adaptedto throttle the flow of water through the inlet duct, said transitionsection having a cross-section which gradually changes from that of thevalve section to that of the merging section, and inlet ducts joiningtogether to form a single composite duct at the merging section, saidcomposite duct including an impeller section, a diffuser section and arudder section, propeller means provided in said impeller section andincluding at least two propellers for inducing a flow of water throughthe duct system, said diffuser section having a cross-section whichgradually changes from that of the impeller section to that of therudder section, and a plurality of rudders provided in the ruddersection.
 13. The ducted propulsion system as claimed in claim 12 inwhich the cross-sectional area of the composite duct is not greater thanthe combined cross-sectional areas of said inlet ducts.
 14. The ductedpropulsion system as claimed in claim 12 in which the two propellers aredisposed in a side by side relationship in said impeller section. 15.The ducted propulsion system as claimed in claim 12 in which the twopropellers are mounted one in front of the other in a staggeredrelationship.
 16. The ducted propulsion system as claimed in claim 12 inwhich there are three propellers in said impeller section, two of thepropellers being disposed in a side by side relationship and the thirdbeing disposed between the other two and out of line with them.
 17. Theducted propulsion system as claimed in claim 12 in which said propellersare contra-rotating.
 18. The ducted propulsion system as claimed inclaim 12 together with sound and vibration absorptive material placedabout the ducts to modulate noise emission.